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<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        Person.prototype.lastName='刘';
        function Person() {
            
        }
        var person1=new Person();
        var person2=new Person();
        console.log(person1.lastName);
        console.log(person2.lastName);
    </script>
</body>
</html>